<!--$Id: env_failchk.so,v 10.7 2007/09/21 20:06:01 bostic Exp $-->
<!--Copyright (c) 1997,2008 Oracle.  All rights reserved.-->
<!--See the file LICENSE for redistribution information.-->
<html>
<head>
<title>Berkeley DB: DB_ENV-&gt;failchk</title>
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++">
</head>
<body bgcolor=white>
<table width="100%"><tr valign=top>
<td>
<b>DB_ENV-&gt;failchk</b>
</td>
<td align=right>
<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a>
<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td>
</tr></table>
<hr size=1 noshade>
<tt>
<b><pre>
#include &lt;db.h&gt;
<p>
int
DB_ENV-&gt;failchk(DB_ENV *dbenv, u_int32_t flags);
</pre></b>
<hr size=1 noshade>
<b>Description: DB_ENV-&gt;failchk</b>
<p>The DB_ENV-&gt;failchk method checks for threads of control (either a true
thread or a process) that have exited while manipulating Berkeley DB library
data structures, while holding a logical database lock, or with an
unresolved transaction (that is, a transaction that was never aborted
or committed).  For more information, see <a href="../ref/cam/app.html">Architecting Data Store and Concurrent Data Store applications</a>, and
<a href="../ref/transapp/app.html">Architecting Transactional Data Store
applications</a>.</p>
<p>The DB_ENV-&gt;failchk method is based on the "thread_id" and "is_alive"
functions specified to the <a href="../api_c/env_set_thread_id.html">DB_ENV-&gt;set_thread_id</a> method.  Applications
calling the DB_ENV-&gt;failchk method must have already called the
<a href="../api_c/env_set_isalive.html">DB_ENV-&gt;set_isalive</a> method, on the same <a href="../api_c/env_class.html">DB_ENV</a>, and must have
configured their database environment using the
<a href="../api_c/env_set_thread_count.html">DB_ENV-&gt;set_thread_count</a> method.</p>
<p>If DB_ENV-&gt;failchk determines a thread of control exited while
holding database read locks, it will release those locks.  If
DB_ENV-&gt;failchk determines a thread of control exited with an
unresolved transaction, the transaction will be aborted.  In either of
these cases, DB_ENV-&gt;failchk will return 0 and the application may
continue to use the database environment.</p>
<p>In either of these cases, the DB_ENV-&gt;failchk method will also report
the process and thread IDs associated with any released locks or
aborted transactions.  The information is printed to a specified output
channel (see the <a href="../api_c/env_set_msgfile.html">DB_ENV-&gt;set_msgfile</a> method for more information), or
passed to an application callback function (see the
<a href="../api_c/env_set_msgcall.html">DB_ENV-&gt;set_msgcall</a> method for more information).</p>
<p>If DB_ENV-&gt;failchk determines a thread of control has exited such
that database environment recovery is required, it will return
<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>.  In this case, the application should not
continue to use the database environment.  For a further description as
to the actions the application should take when this failure occurs, see
<a href="../ref/cam/fail.html">Handling failure in Data Store and
Concurrent Data Store applications</a>, and
<a href="../ref/transapp/fail.html">Handling failure in Transactional
Data Store applications</a>.</p>
<p>The DB_ENV-&gt;failchk method may not be called before the <a href="../api_c/env_open.html">DB_ENV-&gt;open</a> method is called.</p>
<p>The DB_ENV-&gt;failchk method
returns a non-zero error value on failure
and 0 on success.
</p>
<b>Parameters</b> <br>
 <b>flags</b><ul compact><li>The <b>flags</b> parameter is currently unused, and must be set to 0.</ul>
<br>
<br><b>Errors</b>
<p>The DB_ENV-&gt;failchk method
may fail and return one of the following non-zero errors:</p>
<br>
<b>EINVAL</b><ul compact><li>An
invalid flag value or parameter was specified.</ul>
<br>
<hr size=1 noshade>
<br><b>Class</b>
<a href="../api_c/env_class.html">DB_ENV</a>
<br><b>See Also</b>
<a href="../api_c/env_list.html">Database Environments and Related Methods</a>
</tt>
<table width="100%"><tr><td><br></td><td align=right>
<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
</td></tr></table>
<p><font size=1>Copyright (c) 1996,2008 Oracle.  All rights reserved.</font>
</body>
</html>
